/*
 * @(#)NumericConvertFunction.java
 *
 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
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 *
 * You acknowledge that this software is not designed or intended for use in
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 */

package org.wso2.balana.cond;

import org.wso2.balana.ctx.EvaluationCtx;

import org.wso2.balana.attr.AttributeValue;
import org.wso2.balana.attr.DoubleAttribute;
import org.wso2.balana.attr.IntegerAttribute;

import java.util.HashSet;
import java.util.List;
import java.util.Set;

/**
 * A class that implements all the numeric type conversion functions
 * (double-to-integer and integer-to-double). It takes one argument of the
 * appropriate type, converts that argument to the other type, and returns the
 * result. If the argument is indeterminate, an indeterminate result is
 * returned.
 * 
 * @since 1.0
 * @author Steve Hanna
 * @author Seth Proctor
 */
public class NumericConvertFunction extends FunctionBase {

	/**
	 * Standard identifier for the double-to-integer function.
	 */
	public static final String NAME_DOUBLE_TO_INTEGER = FUNCTION_NS
			+ "double-to-integer";

	/**
	 * Standard identifier for the integer-to-double function.
	 */
	public static final String NAME_INTEGER_TO_DOUBLE = FUNCTION_NS
			+ "integer-to-double";

	// private identifiers for the supported functions
	private static final int ID_DOUBLE_TO_INTEGER = 0;
	private static final int ID_INTEGER_TO_DOUBLE = 1;

	/**
	 * Creates a new <code>NumericConvertFunction</code> object.
	 * 
	 * @param functionName
	 *            the standard XACML name of the function to be handled by this
	 *            object, including the full namespace
	 * 
	 * @throws IllegalArgumentException
	 *             if the function is unknwon
	 */
	public NumericConvertFunction(String functionName) {
		super(functionName, getId(functionName), getArgumentType(functionName),
				false, 1, getReturnType(functionName), false);
	}

	/**
	 * Private helper that returns the internal identifier used for the given
	 * standard function.
	 */
	private static int getId(String functionName) {
		if (functionName.equals(NAME_DOUBLE_TO_INTEGER))
			return ID_DOUBLE_TO_INTEGER;
		else if (functionName.equals(NAME_INTEGER_TO_DOUBLE))
			return ID_INTEGER_TO_DOUBLE;
		else
			throw new IllegalArgumentException("unknown convert function "
					+ functionName);
	}

	/**
	 * Returns a <code>Set</code> containing all the function identifiers
	 * supported by this class.
	 * 
	 * @return a <code>Set</code> of <code>String</code>s
	 */
	public static Set getSupportedIdentifiers() {
		Set set = new HashSet();

		set.add(NAME_DOUBLE_TO_INTEGER);
		set.add(NAME_INTEGER_TO_DOUBLE);

		return set;
	}

	/**
	 * Private helper that returns the type used for the given standard
	 * function. Note that this doesn't check on the return value since the
	 * method always is called after getId, so we assume that the function is
	 * present.
	 */
	private static String getArgumentType(String functionName) {
		if (functionName.equals(NAME_DOUBLE_TO_INTEGER))
			return DoubleAttribute.identifier;
		else
			return IntegerAttribute.identifier;
	}

	/**
	 * Private helper that returns the return type for the given standard
	 * function. Note that this doesn't check on the return value since the
	 * method always is called after getId, so we assume that the function is
	 * present.
	 */
	private static String getReturnType(String functionName) {
		if (functionName.equals(NAME_DOUBLE_TO_INTEGER))
			return IntegerAttribute.identifier;
		else
			return DoubleAttribute.identifier;
	}

	/**
	 * Evaluate the function, using the specified parameters.
	 * 
	 * @param inputs
	 *            a <code>List</code> of <code>Evaluatable</code> objects
	 *            representing the arguments passed to the function
	 * @param context
	 *            an <code>EvaluationCtx</code> so that the
	 *            <code>Evaluatable</code> objects can be evaluated
	 * @return an <code>EvaluationResult</code> representing the function's
	 *         result
	 */
	public EvaluationResult evaluate(List inputs, EvaluationCtx context) {

		// Evaluate the arguments
		AttributeValue[] argValues = new AttributeValue[inputs.size()];
		EvaluationResult result = evalArgs(inputs, context, argValues);
		if (result != null)
			return result;

		// Now that we have real values, perform the numeric conversion
		// operation in the manner appropriate for this function.
		switch (getFunctionId()) {
		case ID_DOUBLE_TO_INTEGER: {
			double arg0 = ((DoubleAttribute) argValues[0]).getValue();
			long longValue = (long) arg0;

			result = new EvaluationResult(new IntegerAttribute(longValue));
			break;
		}
		case ID_INTEGER_TO_DOUBLE: {
			long arg0 = ((IntegerAttribute) argValues[0]).getValue();
			double doubleValue = (double) arg0;

			result = new EvaluationResult(new DoubleAttribute(doubleValue));
			break;
		}
		}

		return result;
	}
}
